Diablo 500 Restoration #3 in 2008

My third restoration was to save a 500 from the scrap or being parted out. The chassis, hood, handle bars and ski seater frame came from Chuck G in Urbana, Ohio. The rest of the parts will come from my inventory.

I’m interested in restoring a 500 because they are different from the 502 & 503 in so many ways. For those of you who have purchased the Technical Packets, in that packet is a four page write up explaining all the changes Bolens made between the 1967 and 1968 production. During the restoration, I’ll point out some of these changes.

8/30/08 – Above is the chassis I’m starting with. It is a pretty solid piece overall with some rust but no cracks or major rust. It has a significant dent and bent up right front corner along with several other smaller bends.

The bogie rails and other tubing on a 500 is only 14 gauge which is thinner than the 12 gauge of the 502/503. The deck metal is also thinner material and the deck sides are not formed under toward the bogie assemblies. This makes the deck and frame a delicate piece of steel.

As you will see later, the original 500 only had two bumper brackets. Where the brackets connect, the 500 does not have the additional bracing inside the center frame deck. It did not take Bolens long to realize that this natural handle did not have enough strength to support the weight of the sled, so they reinforced it with bracing and 2 more bumper brackets later in the 500 production year. Along with the light weight design, another issue with the 500 chassis is that the front chassis frame ahead of the gearbox post often bent down which then allowed the hood to settle on top of the gearbox post. Many a 500 hood is dented upward from this pounding down against the gearbox post.

The hood was severely pitted and bowed. Straightening it out was fairly simple. Grinding and sandblasting all the paint and rust off was challenging. After painting, I only then realized I should have covered up some of the heavy pitting as it showed through the finish. The 500 hoods had no air intake louvers or heat shields on the motors which meant the motors ran hot and would vapor lock in the carb. The hoods were also made from lighter gauge sheet metal so they get bent up easily. The hoods do have a bracket on them coming up from the hood mount to stop the hood from hinging over and contacting the bumper which seems like a great idea. However, it was not utilized with the 502 or 503 model.

The gearbox I’m using had the upper bearings fail. It’s a wonder the gearbox did not break up as the chain jumped the tensioner sprocket and locked up yanking the input shaft down toward the sprockets. Gearboxes on the 500 are much more delicate than the 502/3 gearbox. Different gear ratios, lighter aluminum housing and a weak surface for mounting the tensioning sprocket to meant these gearboxes often cracked.

Two more things to note is the 500 did not have the rubber pad around the gearcase opening or a rubber pad under the fuel tank. Having no rubber around the gearcase allowed snow to enter the engine compartment between the deck and the chaincase. Without the rubber pad under the fuel tank, I suspect the tank got damaged by steel on steel construction. These were corrected with the 502/503.

Shown above right is the long nose tin and 2-bracket design for the bumper. Very weak. Later in the same production year, Bolens shortened up the front nose tin just a little and installed two more brackets. Later on the 502/3, they shortened up the nose tin even more for a more stable front end.

Handle bars on the 500 are weak and shortly after they were in the field, a Service Bulletin came out to install factory gussets. The dash is made of very thin plastic and often gets damaged and cracked. Above is a dash in excellent condition.

Ski Seater frames on the 500 do not have the handle bars that route around the back side of the sleigh.

We resurrected an original seat cover for this restoration. As bad and stiff as the cover was, we used some Blue Magic Cleaner and Conditioner and the cover turned out great.

The seat received a new wooden frame and the original foam was reused. The skis installed were a pair of Barrie G’s skis and the trademark 500 “2 two clip” design was installed.

We went all out on this restoration with a chrome grille and newly chromed bumper along with newly chromed brake and throttle handles. A typical grille would have the inner area painted black, but I could not bring myself to cover up this chrome nose cone.

The engine was torn apart and like many, needed a piston. A fresh coat of paint, new gaskets and seals, new ignition components and a new piston and the engine was ready to run. It is equipped with a HR3A Tillotson which was standard on the Diablo 300 cc Hirth Motor. The motor mounts (top and bottom) are different than the 502.

This Diablo was restored at the same time as another Diablo 502. I found that restoring two at once does not take as long as two separately. With the exception of how the hood finished, I was very happy with this restoration.

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